The invention relates to the field of rotary piston fluid flow devices in which fluid flow is caused to occur with respect to the device in response to the positive displacement pumping action of a plurality of pistons which move along a rotary path with the outer face portion of each piston adjacent the inner facing surface of the annular housing of the device. More in particular, the invention relates to a rotary piston internal combustion engine in which a charge compressed by a rotary piston is ignited to provide pressured products of combustion. The products of combustion are expanded, thereby providing a rotary driving force to the piston. The connecting of the rotary piston to a drive shaft within the engine causes the rotary piston when subjected to a driving force to apply torque to the engine drive shaft, thereby driving it in rotation. The rotary piston internal combustion engine of the invention has an operating cycle similar to that of a reciprocating piston engine and includes the events of intake, compression, combustion followed by expansion, and exhaust. Specifically, devices with rotary sliding pistons are disclosed in applicant's U.S. Application Ser. No. 851,485, now U.S. Pat. No. 4,144,866, as follows: U.S. Pat No. 3,950,117 which issued on Apr. 13, 1976 to Artajo; U.S. Pat. No. 3,349,757 which issued on Oct. 31, 1967 to Artajo; U.S. Pat. No. 3,289,654 which issued on Dec. 6, 1966 to Geiger; and U.S. Pat. No. 3,442,257 which issued on May 6, 1969 to Walker.